1. Field of the Invention
The present invention relates to a Network Sharing (NS) system. More particularly, the present invention relates to a method and apparatus for informing a Radio Access Network (RAN) of a selected Core Network (CN) operator from a User Equipment (UE).
2. Description of the Related Art
A mobile communication system basically includes a RAN and a UE. The RAN has a Node B and is connected to a second network through a CN. RANs, which are operated by different operators or use different radio access techniques, can be connected to a plurality of CNs operated by the same or different CN operators. Sharing a RAN among different CN operators is called network sharing.
In a Code Division Multiple Access (CDMA) cellular mobile communication system, a RAN includes a Base Transceiver Subsystem (BTS) and a Base Station Controller (BSC). The RAN is connected to a CN with a Mobile Switching Center (MSC). Meanwhile, in a Global System for Mobile communications (GSM)-based Wideband CDMA (WCDMA) system, that is, Universal Mobile Telecommunications System (UMTS), a RAN includes a Node B and a Radio Network Controller (RNC) and is connected to a CN with a Serving General Packet Radio Service (GPRS) Support Node (SGSN).
CN operators are identified by Public Land Mobile Network (PLMN) Identifies (ids). A PLMN id is a combination of a Mobile Country Code (MCC) and a Mobile Network Code (MNC). A UE selects a PLMN id identifying a desired CN operator for itself or under the control of the network. To access the selected CN, the UE needs to notify the PLMN id of the RAN.
Since conventionally, there are no procedures specifying as to when and how the UE is to transmit a selected PLMN id to the RAN, the RAN cannot perform accurate routing to a selected CN for the UE.
Accordingly, there is a need for a specific signaling procedure by the UE for informing the RAN of a selected PLMN id to be transmitted.